The present invention pertains to the area of viewing screens and methods for fabricating viewing screens for display devices and, more particularly, to a viewing screen for a field emission display and method for the fabrication thereof.
Methods for fabricating viewing screens having black surround on a glass substrate are known in the art. It is known in the art to fabricate a black surround material using glass binders and pigments. These materials are known to have linear thermal expansion coefficients within a range of about 10xc3x9710xe2x88x926 to 12xc3x9710xe2x88x926xc2x0 C.xe2x88x921. The prior art black surround materials are adequate for the combinations of temperature and type of glass substrate utilized in prior art methods for fabricating viewing screens. For example, prior art methods typically expose the black surround and the glass substrate to temperatures of up to 550xc2x0 C.
However, it may be desirable to utilize higher temperatures, at which the prior art combinations of black surround and glass substrate may be inadequate. For example, it is believed to be desirable in the fabrication of field mission displays to utilize process temperatures up to about 600xc2x0 C. First, the glass substrate must be able to withstand. such temperatures. Furthermore, the black surround-substrate interface must not crack during the heat treatments.
However, prior art viewing screens may not be adequate for repeated high temperature treatments. For example, they may have temperature tolerances that are less than these higher temperatures. Soda lime silicate is a typical glass substrate, which can tolerate temperatures up to only 540xc2x0 C. Furthermore, even if the glass can withstand the higher temperature, a mismatch of the thermal expansion coefficients of the black surround material and the glass substrate can undesirably result in the cracking of the black surround-substrate interface.
For example, it is known to use borosilicate glass for the glass substrate in field emission displays. It is believed to be desirable to increase processing temperatures up to about 600xc2x0 C. Borosilicate glass can withstand these higher processing temperatures. However, borosilicate glass has a thermal expansion coefficient equal to about 4xc3x9710xe2x88x926xc2x0 C.xe2x88x921, which is appreciably less than that of the standard thick-film black surround. Thus, if the standard thick-film black surround is used on the borosilicate glass, the black surround-substrate interface cracks during high temperature thermal cycling.
Accordingly, there exists a need for an improved method for fabricating a viewing screen for a display device, which provides a viewing screen that maintains its physical integrity at temperatures up to at least 550xc2x0 C.